Background

Protein-bound polysaccharide (PSK) has been used in traditional Chinese medicine (TCM) since the Ming Dynasty of China.

In the 1980s, the Japanese government approved the use of PSK for treating several types of cancers. By 1984, it ranked 19th on the list of the world's most commercially successful drugs with annual sales of $255 million.

PSK is obtained from cultured mycelia of the Coriolus versicolor, a mushroom thought to have antimicrobial, antiviral, and antitumor properties.

PSK extracts are available for clinical use in Japan, where it is widely used for cancer immunochemotherapy. In Japan, PSK is currently used as a cancer treatment, in conjunction with surgery, chemotherapy, and/or radiation. Its active ingredient can be administered as a tea or in oral capsule form. In the United States, a similar product is labeled simply Coriolus versicolor extract. Coriolus versicolor is available in limited supply in U.S. markets. In Japan, PSK is currently the best-selling cancer medicine.

Evidence

Uses based on scientific evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare professional.

PSK in addition to chemotherapy and surgery has been associated with increased disease-free survival rate for patients with colorectal cancer in various clinical trials as opposed to these pharmaceutical drugs alone. Well-designed clinical trials are needed to confirm these results along with optimal dosing regimens and optimal pharmaceutical combinations. PSK does not seem to affect the cure rate of colon cancer.

C

Esophageal cancer (adjuvant)

A small number of clinical trials have examined the ability of PSK, in conjunction with chemotherapy and radiation, to increase survival time in esophageal cancer. Further well-designed trials are needed to fully understand PSK's potential therapeutic role in esophageal cancer.

C

Gastric cancer (adjuvant)

Several clinical trials or case studies have investigated the use of PSK in combination with chemotherapy in the treatment of gastric cancer. Results from many of the clinical trials show that PSK administered along with chemotherapy is associated with increased 2-5 year survival rates. However, some trials found no significant effect on survival over this same period of time. No significant increase in survival has been shown in long-term (greater than five years) studies.

C

Leukemia (adjuvant)

One preliminary human trial in patients with acute leukemia suggests that adjunct PSK therapy may prolong duration of remission and survival time. In a second study in patients with acute nonlymphocytic leukemia, no significant increases in survival were found. Well-designed clinical trials are required in order to determine if PSK therapy may in fact prolong remission and increase survival time in individuals with acute leukemia.

C

Liver cancer (adjuvant)

Study results of PSK as an adjunct therapy for liver cancer yield mixed results. Well-designed clinical trials are needed to determine the role of PSK on survival time and remission in individuals with liver cancer.

C

Lung cancer (adjuvant)

PSK has been studied as an adjuvant therapy in lung cancer patients. Further research is needed before a conclusion can be drawn.

C

Nasopharyngeal carcinoma (adjuvant)

In preliminary human studies, PSK, used as adjuvant treatment to radiotherapy with or without chemotherapy, has been shown to increase the five-year survival rate following treatment. Well-designed clinical trials, with larger patient numbers, are needed to confirm these results.

C

Breast cancer (adjuvant)

The available evidence does not support the use of PSK, in conjunction with hormone therapy, chemotherapy, and/or surgery, to increase survival rates in breast cancer patients.

D

*Key to grades:

A: Strong scientific evidence for this use;B: Good scientific evidence for this use; C: Unclear scientific evidence for this use;D: Fair scientific evidence against this use (it may not work);F: Strong scientific evidence against this use (it likely does not work).

For full grading rationale, click here.

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified health care professional

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy. Consult a healthcare professional immediately if you experience side effects.

Allergies

Avoid in individuals with a known allergy/hypersensitivity to PSK, Coriolus versicolor, or any of its constituents.

Side Effects and Warnings

PSK generally seems to have a low incidence of mild and tolerable side effects. In one report, three cases of toxicity were noted, and PSK was discontinued. PSK has been associated with side effects of gastrointestinal upsetand darkening of the fingernails, but these effects have been limited and general safety has been demonstrated with daily oral doses for extended periods. Darkening of the fingernails and coughing have been reported during the administration of the powder drug.

Low blood cell counts including leukopenia, thrombocytopenia, and albuminuria (protein in the urine) were observed in two clinical trials. It should be noted that patients also received chemotherapy in addition to PSK in these trials, which may have contributed.

Use cautiously in patients with coronary artery disease due to antiangiogenic properties (inhibition of new blood vessel growth) in the heart.

Pregnancy and Breastfeeding

Not recommended due to lack of sufficient data.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy.

Interactions with Drugs

Liver function impairment and toxicity has been reported. Caution is advised when taking PSK with other agents that are broken down by the liver due to increased risk of side effects.

Antiangiogenic properties (inhibition new blood vessel growth) have been proposed. In theory, there could be an additive effect when PSK is taken in conjugation with other known antiangiogenic agents, such as leflunomide.

Thrombocytopenia (low blood platelet count) has been reported. Theoretically, this could increase the risk of bleeding. Leukopenia and albuminuria were also observed in two clinical trials. It should be noted that patients also received chemotherapy in addition to PSK in these trials. These effects may be attributed to either PSK or chemotherapy.

Numerous animal and human studies have demonstrated that PSK may improve survival time in patients with lung cancer, gastric cancer, stomach cancer, colon cancer, and leukemia when used in conjunction with chemotherapy. This may be a positive interaction, although additional study is needed to confirm this finding.

PSK in immunochemotherapy has been used in combination with hormone therapy to treat pancreatic cancer; therefore, additive effects are possible.

Interactions with Herbs and Dietary Supplements

Liver function impairment and toxicity has been reported. Caution is advised when taking PSK with other agents that are broken down by the liver due to increased risk of side effects.

Antiangiogenic properties (inhibition of new blood vessel growth) have been proposed. In theory, there could be an additive effect when PSK is taken in conjugation with other known antiangiogenic herbs and supplements such as shark cartilage, horse chestnut, feverfew, and bilberry.

Thrombocytopenia (low blood platelet count) has been reported. Theoretically, this could increase the risk of bleeding. Leukopenia and albuminuria were also observed in two clinical trials. It should be noted that patients also received chemotherapy in addition to PSK in these trials. These effects may be attributed to either PSK or chemotherapy.

PSK in immunochemotherapy has been used in combination with hormone therapy to treat pancreatic cancer; therefore, additive effects are possible.

Theoretically, PSK may have a synergistic effect with other immunotherapeutic herbs and supplements. Numerous animal and human studies have demonstrated PSK improves survival time in patients with lung cancer, gastric cancer, stomach cancer, colon cancer, and leukemia when used in conjunction with chemotherapy.

Authors

This information is based on a professional level monograph edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Selected References

Natural Standard developed the above evidence-based information based on a systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.